diff --git a/CMakeLists.txt b/CMakeLists.txt
index ad007fe4..02dcd3bc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -175,6 +175,7 @@ set(STA_SOURCE
   search/PathVertexRep.cc
   search/Power.cc
   search/Property.cc
+  search/ReadVcdActivities.cc
   search/ReportPath.cc
   search/Search.cc
   search/SearchPred.cc
diff --git a/search/ReadVcdActivities.cc b/search/ReadVcdActivities.cc
new file mode 100644
index 00000000..fa782ad3
--- /dev/null
+++ b/search/ReadVcdActivities.cc
@@ -0,0 +1,138 @@
+// OpenSTA, Static Timing Analyzer
+// Copyright (c) 2022, Parallax Software, Inc.
+// 
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+#include "ReadVcdActivities.hh"
+
+#include "VcdReader.hh"
+#include "Debug.hh"
+#include "Network.hh"
+#include "VerilogNamespace.hh"
+#include "ParseBus.hh"
+#include "Sdc.hh"
+#include "Power.hh"
+#include "Sta.hh"
+
+namespace sta {
+
+using std::min;
+using std::swap;
+using std::to_string;
+
+static void
+setVcdActivities(Vcd &vcd,
+                 Sta *sta);
+static void
+setPinActivity(const char *pin_name,
+               int transition_count,
+               float activity,
+               float duty,
+               Debug *debug,
+               Network *network,
+               Power *power);
+void
+readVcdActivities(const char *filename,
+                  Sta *sta)
+{
+  Vcd vcd = readVcdFile(filename, sta);
+  setVcdActivities(vcd, sta);
+}
+
+static void
+setVcdActivities(Vcd &vcd,
+                 Sta *sta)
+{
+  Debug *debug = sta->debug();
+  Network *network = sta->network();
+  Power *power = sta->power();
+
+  float clk_period = 0.0;
+  for (Clock *clk : *sta->sdc()->clocks())
+    clk_period = min(clk->period(), clk_period);
+
+  VarTime time_max = vcd.timeMax();
+  for (VcdVar &var : vcd.vars()) {
+    const VcdValues &var_values = vcd.values(var);
+    if (!var_values.empty()) {
+      int transition_count = 0;
+      char prev_value = var_values[0].value();
+      VarTime prev_time = var_values[0].time();
+      VarTime high_time = 0;
+      for (const VcdValue &var_value : var_values) {
+        VarTime time = var_value.time();
+        char value = var_value.value();
+        if (prev_value == '1')
+          high_time += time - prev_time;
+        transition_count++;
+        prev_time = time;
+        prev_value = value;
+      }
+      if (prev_value == '1')
+        high_time += time_max - prev_time;
+      float duty = static_cast<float>(high_time) / time_max;
+      float activity = transition_count
+        / (time_max * vcd.timeUnitScale() / clk_period);
+
+      string var_name = var.name();
+      if (var_name[0] == '\\')
+        var_name += ' ';
+      const char *sta_name = verilogToSta(var_name.c_str());
+      if (var.width() == 1) {
+        setPinActivity(sta_name, transition_count, activity, duty,
+                       debug, network, power);
+      }
+      else {
+        char *bus_name;
+        int from, to;
+        parseBusRange(sta_name, '[', ']', '\\',
+                      bus_name, from, to);
+        if (from > to)
+          swap(from, to);
+        for (int bit = from; bit <= to; bit++) {
+          string name = bus_name;
+          name += '[';
+          name += to_string(bit);
+          name += ']';
+          setPinActivity(name.c_str(), transition_count, activity, duty,
+                       debug, network, power);
+        }
+      }
+    }
+  }
+}
+
+static void
+setPinActivity(const char *pin_name,
+               int transition_count,
+               float activity,
+               float duty,
+               Debug *debug,
+               Network *network,
+               Power *power)
+{
+  Pin *pin = network->findPin(pin_name);
+  if (pin) {
+    debugPrint(debug, "vcd_activities", 1,
+               "%s transitions %d activity %.2f duty %.2f",
+               pin_name,
+               transition_count,
+               activity,
+               duty);
+    power->setUserActivity(pin, activity, duty,
+                           PwrActivityOrigin::user);
+  }
+}
+
+}
diff --git a/search/ReadVcdActivities.hh b/search/ReadVcdActivities.hh
new file mode 100644
index 00000000..e79f5cf4
--- /dev/null
+++ b/search/ReadVcdActivities.hh
@@ -0,0 +1,27 @@
+// OpenSTA, Static Timing Analyzer
+// Copyright (c) 2022, Parallax Software, Inc.
+// 
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+// 
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+// 
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+#pragma once
+
+namespace sta {
+
+class Sta;
+
+void
+readVcdActivities(const char *filename,
+                  Sta *sta);
+
+} // namespace
diff --git a/search/Vcd.hh b/search/Vcd.hh
index 33e66304..b0475fe2 100644
--- a/search/Vcd.hh
+++ b/search/Vcd.hh
@@ -37,7 +37,7 @@ typedef vector<VcdValue> VcdValues;
 typedef int64_t VarTime;
 typedef vector<string> VcdScope;
 
-enum class VcdVarType { wire, reg, parameter };
+enum class VcdVarType { wire, reg, parameter, real };
 
 class Vcd : public StaState
 {
@@ -54,6 +54,7 @@ public:
   double timeScale() const { return time_scale_; }
   void setTimeScale(double time_scale);
   const string &timeUnit() const { return time_unit_; }
+  double timeUnitScale() const { return time_unit_scale_; }
   void setTimeUnit(const string &time_unit,
                    double time_unit_scale);
   VarTime timeMax() const { return time_max_; }
@@ -127,4 +128,4 @@ private:
   uint64_t bus_value_;
 };
 
-}
+} // namespace
diff --git a/search/VcdReader.cc b/search/VcdReader.cc
index 33411f25..ed08b63a 100644
--- a/search/VcdReader.cc
+++ b/search/VcdReader.cc
@@ -21,7 +21,6 @@
 #include "Zlib.hh"
 #include "Report.hh"
 #include "StringUtil.hh"
-#include "StaState.hh"
 
 namespace sta {
 
@@ -170,6 +169,8 @@ VcdReader::parseVar()
       type = VcdVarType::reg;
     else if (type_name == "parameter")
       type = VcdVarType::parameter;
+    else if (type_name == "real")
+      type = VcdVarType::real;
     else
       report_->fileError(803, filename_, stmt_line_,
                          "Unknown variable type %s.",
@@ -221,33 +222,35 @@ VcdReader::parseVarValues()
 {
   string token = getToken();
   while (!token.empty()) {
-    if (token[0] == '#') {
+    char char0 = toupper(token[0]);
+    if (char0 == '#') {
       prev_time_ = time_;
       time_ = stoll(token.substr(1));
       if (time_ > prev_time_)
         vcd_->setMinDeltaTime(min(time_ - prev_time_, vcd_->minDeltaTime()));
     }
-    else if (token[0] == '0'
-             || token[0] == '1'
-             || token[0] == 'X'
-             || token[0] == 'U'
-             || token[0] == 'Z') {
+    else if (char0 == '0'
+             || char0 == '1'
+             || char0 == 'X'
+             || char0 == 'U'
+             || char0 == 'Z') {
       string id = token.substr(1);
       if (!vcd_->varIdValid(id))
         report_->fileError(804, filename_, stmt_line_,
                            "unknown variable %s", id.c_str());
-      vcd_->varAppendValue(id, time_, token[0]);
+      vcd_->varAppendValue(id, time_, char0);
     }
-    else if (token[0] == 'b') {
-      if (token[1] == 'X'
-          || token[1] == 'U'
-          || token[1] == 'Z') {
+    else if (char0 == 'B') {
+      char char1 = toupper(token[1]);
+      if (char1 == 'X'
+          || char1 == 'U'
+          || char1 == 'Z') {
         string id = getToken();
         if (!vcd_->varIdValid(id))
           report_->fileError(804, filename_, stmt_line_,
                              "unknown variable %s", id.c_str());
         // Bus mixed 0/1/X/U not supported.
-        vcd_->varAppendValue(id, time_, token[1]);
+        vcd_->varAppendValue(id, time_, char1);
       }
       else {
         string bin = token.substr(1);
@@ -330,8 +333,7 @@ reportVcdWaveforms(const char *filename,
                    StaState *sta)
 
 {
-  VcdReader reader(sta);
-  Vcd vcd = reader.read(filename);
+  Vcd vcd = readVcdFile(filename, sta);
   reportWaveforms(vcd, sta->report());
 }
 
diff --git a/tcl/Power.tcl b/tcl/Power.tcl
index 2b611955..bdd9ba42 100644
--- a/tcl/Power.tcl
+++ b/tcl/Power.tcl
@@ -246,6 +246,11 @@ proc set_power_activity { args } {
   }
 }
 
+################################################################
+
+# Defined in StaTcl.i
+define_cmd_args "read_vcd_activities" { filename }
+
 proc power_find_nan { } {
   set corner [cmd_corner]
   foreach inst [network_leaf_instances] {
diff --git a/tcl/StaTcl.i b/tcl/StaTcl.i
index e5f5445f..7a261763 100644
--- a/tcl/StaTcl.i
+++ b/tcl/StaTcl.i
@@ -81,6 +81,7 @@
 #include "search/ReportPath.hh"
 #include "search/Power.hh"
 #include "search/VcdReader.hh"
+#include "search/ReadVcdActivities.hh"
 
 namespace sta {
 
@@ -5008,6 +5009,12 @@ set_power_pin_activity(const Pin *pin,
 					      PwrActivityOrigin::user);
 }
 
+void
+read_vcd_activities(const char *filename)
+{
+  readVcdActivities(filename, Sta::sta());
+}
+
 ////////////////////////////////////////////////////////////////
 
 EdgeSeq *